Conversion of three-phase AC power to DC power is frequently accomplished with bridge circuits utilizing solid state switching devices, such as insulated gate bipolar transistors (IGBTs). In some applications, such as certain applications for providing power to elevators, for returning regenerative power from the elevator to the power grid, bidirectional switch modules may be employed, each module including a controllable solid state switch (such as an IGBT) having an anti-parallel diode connected thereacross in series with an oppositely poled switch and diode, in a common electrode configuration (either common emitter or common collector). As is known, during commutation from switch to switch which provides the desired DC voltage, load and circuit inductances tend to maintain current flow as the switch ceases conducting, the inductances within the bridge circuitry thereby creating large inductive reaction back voltages across the turned-off switch. Frequently, the back voltages will exceed the reverse voltage capacity of a switch. Therefore, clamp circuits have been known to prevent high reverse voltages upon switch turnoff. One such circuit is illustrated in FIG. 1, in which, by way of example, an IGBT 8 and its anti-parallel diode 9 are connected in common emitter configuration with an IGBT 10 and an anti-parallel diode 11. A clamp 12 for the bidirectional switch module 7 consists of four diodes 13-16, a capacitor 19 and a resistor 20. Consider the case when the IGBT 8 is conducting: current flows downwardly through it and down through the diode 11. Since the IGBT 8 and diode 11 constitute essentially short circuits, no current flows through the clamp 12. When the IGBT 8 is turned off, current can no longer flow therethrough, so it flows through the diode 14, the capacitor 19 and resistor 20, and the diode 15. The reverse voltage is built up across the capacitor 19, which eventually dissipates all of the energy through the resistor 20. In order for this device to be operable, it must be able to dissipate all of the energy that may be stored in the capacitor 19 prior to the next commutation event. Instead of acting as a snubber to cause the voltage of the capacitor to return to zero volts after each commutation event, if the device were operated as a regulated clamp, the back voltage across each IGBT, when turned off, could be maintained at a voltage just below the reverse voltage rating for the IGBT. However, in order to do so, a separate regulator would have to be supplied for each of the clamps 12 in the circuit. In fact, a clamp of the type shown in FIG. 1 is useful only for very low power applications.